Trivia

"Death embodies decay and can possess the soul of a living being. Often taking the form of a woman, Death can manipulate reality, time, and space, and came into existence at the same time as Entropy, Eternity, and Infinity. Immortals are immune to Death's ability. Thanos wanted to rule the universe with Death. In an attempt to impress her, he killed all life in half of the universe with the snap of his fingers."[3]

In an interview, Josh Brolin expanded on Thanos' relationship with Death, and confirmed that Death will be portrayed as a woman in the Marvel Cinematic Universe: "His relationship with Death, who is actually the woman, I love that. You can take Sin City (in which Brolin plays a man obsessed with a dark-hearted woman) and pump it full of steroids, and then you have Thanos. I like that he’s motivated by that — not just motivated by destruction or death or this or that. He’s motivated by a very identifiable, human trait."[4]

Hive, a powerful Inhuman who HYDRA reveres, was referred to as "Death" due to its fearsome nature and reputation.